一维损伤对低含水率膨胀土强度和变形的影响

对3组15个不同破损孔径的一维损伤膨胀土圆柱试样,进行控制净围压分别为50,100,150kPa的三轴剪切试验,研究低含水率(w=7%)条件下一维圆柱孔破损重塑膨胀土的应力-应变特性、体变特性以及破损形态.试验结果发现:与以往常规含水率(约20%)土样不同,破损孔径对膨胀土强度没有显著的弱化或者是强化作用,相同破损面积的试样之间也未表现出相似的强度和变形特征;揭示了既有破损对土体峰值强度的影响与土体的含水率密切相关.试样整体表现出先剪缩后剪胀的特性,但随着围压的提高,剪缩阶段明显缩短;从破坏形态可以看出,随着围压的提高,裂隙长度变短、倾角变小,说明围压对既有裂隙的扩展有明显的抑制作用.

The Influence of One-Dimensional Damage on the Strength and Deformation of Low Moisture Content of Expansive Soil

In order to research the stress-strain properties, volumetric strain characteristics and one-dimensional damage morphologies of reconstituted expansive soils with cylindrical-hole damage at low moisture content (w=7%), 15 different cylindrical-pore damaged expansive soil samples were divided into three groups, under the net confining pressure of 50 kPa, 100 kPa and 150 kPa, respectively. Then, triaxial tests were conducted. The results showed that differing from the past conventional studies (i.e. w was about 20%), soil strength was not obviously weakened nor reinforced, and samples with the same pore area did not show similar strength as well as deformation characteristics, revealing that soil peak strength influenced by the damage is closely related to its water content. Generally, soil samples showed a property of shearing shrinkage first, and then dilation. Furthermore, the shearing shrinkage stage was shortened significantly along with the increase in net confining pressure. Observed from the morphology of cracks, the length of fissure was shortened, and the inclination of the cracks became smaller as the confining pressure increased, which indicated that net confining pressure has a significant restraining effect on the development of cracks.